Is it possible to measure the frequency of an LCD monitor without a high-speed video camera?

Question

Monitors

The documentation for the monitor says that it supports a maximum of 76 Hz, but at a lower resolution I managed to set the frequency to 150 Hz. If you increase the frequency by at least 1 Hz, for example, set it to 151 Hz, then the monitor turns off and writes "Out of range".
It turns out the monitor can produce 150 Hz. Is it real 150Hz? Is there a way to check how real they are without a high speed video camera?

Answer 1

I came up with a very simple solution, how to measure the frequency to the hundredth without any tools at all, except for a calculator:
You need to take a SMALL object and quickly move it around the screen. When moving quickly, a clear stepping will be visible, i.e. you will see not one object, but, as it were, many copies of it at once. There is a certain distance between these copies. You can measure this distance, and if the speed of movement of the object is uniform, then you can calculate the frequency of the monitor using the formula (speed / distance), where speed is the speed of the object in pixels per second, and distance is the distance between copies of the object in pixels.
For measurements, you need a ruler, eyes and a calculator, but instead of using a ruler, you can simply count the number of copies of an object on the screen, then only eyes and a calculator remain.
I tried the method in practice:
Can someone advise what tools can be used to rewrite the program so that you can be sure that the animation is not cut?
PS. Some may wonder how I was able to measure the frequency with such high accuracy without even using a ruler. The fact is that I selected such a speed that the speed of the object was a multiple of the screen frequency. As a result, at this moment, 7 copies of the object seem to freeze in place, while constantly flickering. In the end, I just divided the width of the field in which the object moved by 7, and got the distance between the objects WITH VERY HIGH ACCURACY.
PS. The speed of the object was also set with maximum accuracy, because. I made my program in HTML + js, and there you can get the current time accurate to microseconds, and based on the time when rendering the animation, you can accurately calculate the position of the object.
PS. Additionally, I measured at 72 Hz. I got 17 copies of the object, which gave a result of 72.00042 Hz. But of these 17 copies of the object, not all of them were displayed: every 5 copies there was an empty space, which moved to the right at a certain speed. This means that 1 out of 6 frames is thrown out, which eventually gives us a frequency of 60.00035 Hz. It turns out that in fact the frequency of the monitor is not 72 Hz, but only 60 Hz, although the monitor specification states that it can operate at up to 76 Hz (although, as I said above, this may not be the fault of the monitor, but of the browser, which can cut animation up to 60 frames per second).
PS. If your copies are constantly jumping, and adjusting the speed does not help, then adjust the width of the field in which the object moves so that it is a multiple of the speed divided by the expected frequency. If this does not help, you may have a bad timer that does not fire at regular intervals, or these intervals are too long. Width selection by the way can bring your results closer to the expected ones, but I got an accuracy of 0.01 Hz even without width selection.

Answer 2

I measured the flickering frequency of the screen backlight, including on TVs in shopping centers. I noticed that it correlates with the maximum refresh rate - on a TV with a declared 100 Hz it flickers at 100 Hz, where 200, 400, 800 is written - it flickers at 200. Sometimes 60/120/240 TV sets met.
Monitors mostly met 120 / 240 Hz It
is more difficult to measure the refresh rate of the display itself, people with cameras bothered - if you set a short shutter speed and take a picture of a rapidly flickering screen, you can roughly estimate the response time
https://habrahabr.ru/post/225829/